The present invention generally relates to video signal recording and reproducing apparatuses including a noise reduction circuit, and more particularly to a video signal recording and reproducing apparatus which carries out recording and reproduction so that, a reproduced video signal obtained through a noise reduction circuit which reduces a noise component in the reproduced video signal by using line correlations, includes a video signal component which has no line correlation and has a level of a range approximately equal to the range of the level of a video signal component which has no line correlation and is included within an original video signal.
Generally, a video signal recording and reproducing apparatus, such as a video tape recorder, is designed to obtain a reproduced video signal through a noise reduction circuit which is located in a reproducing system. The noise reduction circuit reduces a noise component which is mixed into the reproduced video signal during the reproducing process of the video signal. As is well known, there are the so-called line correlations in the video signal. In other words, video information contents of mutually adjacent horizontal scanning lines are extremely similar to each other. That is, a line correlation exists between the video information contents with an interval of one horizontal scanning period (1H). On the other hand, there is no line correlation in the noise component because the noise component is generated at random. Accordingly, the above noise reduction circuit uses the line correlations in the video signal and obtains the noise component by delaying the reproduced video signal by 1H, and by passing the reproduced video signal and the delayed reproduced video signal through a differential amplifier.
A subtraction is then performed in a subtracting circuit, between the noise component from the differential amplifier and the reproduced video signal, so as to cancel the noise component within the reproduced video signal.
However, not all of the video information have the line correlation. For example, a video information related to a line which extends in a direction other than the vertical direction of the picture and a video information related to a rapidly moving picture do not have the line correlation. Hence, in addition to the noise component, the output signal of the differential amplifier in the above noise reduction circuit also includes the video signal component which has no line correlation. As a result, the subtracting circuit within the noise reduction circuit will also perform a subtraction between the video signal component which has no line correlation and is included within the reproduced video signal and the video signal component which has no line correlation and is included within the output signal of the differential amplifier. For this reason, in order to further improve the signal-to-noise (S/N) ratio of the reproduced video signal, a limiting level for the output signal of the differential amplifier which is supplied to the subtracting circuit will have to be increased. However, if the limiting level for the output signal of the differential amplifier is increased, the video signal component which has no line correlation will also be greatly reduced. Consequently, the blur or unclearness around the contours of the displayed contents in the reproduced picture will become visually conspicuous. Therefore, it was impossible to sufficiently improve the S/N ratio of the reproduced video signal in the conventional video signal recording and reproducing apparatus.